There are a variety of methods known to form hook materials for hook and loop fasteners. One of the first manufacturing methods for forming hooks involved weaving loops of monofilaments into a fibrous or film backing or the like followed by cutting the filament loops to form hooks. These monofilament loops were also heated to form headed structures such as disclosed in U.S. Pat. Nos. 4,290,174; 3,138,841 or 4,454,183. These woven hooks are generally durable and work well for repeated uses. However, they are generally expensive and coarse to the touch.
For use in disposable garments and the like, it was generally desirable to provide hooks that were inexpensive and less abrasive. For these uses and the like, the solution was generally the use of continuous extrusion methods that simultaneously formed the backing and the hook elements, or precursors to the hook elements. With direct extrusion molding formation of the hook elements, see for example U.S. Pat. No. 5,315,740, the hook elements must continuously taper from the backing to the hook tip to allow the hook elements to be pulled from the molding surface. This generally inherently limits the individual hooks to those capable of engaging only in a single direction while also limiting the strength of the engaging head portion of the hook element.
An alternative direct molding process is proposed, for example, in U.S. Pat. No. 4,894,060, which permits the formation of hook elements without these limitations. Instead of the hook elements being formed as a negative of a cavity on a molding surface, the basic hook cross-section is formed by a profiled extrusion die. The die simultaneously extrudes the film backing and rib structures. The individual hook elements are then formed from the ribs by cutting the ribs transversely followed by stretching the extruded strip in the direction of the ribs. The backing elongates but the cut rib sections remain substantially unchanged. This causes the individual cut sections of the ribs to separate from each from the other in the direction of elongation forming discrete hook elements. Alternatively, using this same type extrusion process, sections of the rib structures can be milled out to form discrete hook elements. With this profile extrusion, the basic hook cross section or profile is only limited by the die shape and hooks can be formed that extend in two directions and have hook head portions that need not taper to allow extraction from a molding surface. This profile extrusion is extremely advantageous in providing higher performing and more functionably versatile hook structures. However, a limitation with this method of manufacture is that the orientation of the film backing to form the hook elements results in decreased tear resistance of the hook in the direction of orientation, which generally is the direction of the ribs. As such, there is a need to improve this process so as to allow for production of hook elements where the backing has increased tear resistance.